Study On Elastoplastic Contact Stiffness Characteristics Of Dry Gas Seal Based On Fractal Theory

As one of the more advanced sealing technologies at home and abroad,dry gas sealing technology is widely used in some high-tech fields such as aerospace and nuclear power.However,in the actual situation,in the starting and st opping stages of the dry gas seal friction pair,due to the weak dynamic pressure effect of the friction pair,the resulting air film has insufficient rigidity,resulting in the mutual contact wear between the friction pairs.In addition,due to manufacturing and installation errors,external excitation,frictional contact excitation and gas film self-excitation,it will cause axial and angular vibration of the sealing ring,which will cause frictional vibration of the end face and reduce the sealing and reliability of dry gas seals.Even under the continuous accumulation of these factors,the equipment will become unstable,which will directly lead to the failure of the dry gas sealing system and cause great harm.Scholars at home and abroad have carried out a lot of research on the contact characteristics of friction pairs,but due to the complex and variable nonlinear characteristics of friction pairs,theoretical modeling and numerical modeling become difficult,resulting in many defects of existing contact models.with deficiencies.Therefore,this paper fully considers the elastic-plastic deformation stage when the dynamic and static rings are in frictional contact,establishes a theoretical model of dry gas seal friction contact from the mechanism,and explores the influence of its influencing factors on the dry gas seal contact stiffness through numerical analysis.The established model is verified both theoretically and experimentally,which provides a theoretical basis for the optimization of dry gas seal structure.The main research contents and conclusions of this paper are as follows:A contact model considering the elastic-plastic deformation stage is established.Fully considering the characteristics of asperities satisfying continuity and smoothness in the elastoplastic deformation stage,the cosine function was used to explore the elastoplastic deformation stage of the asperities,and the theoretical contact model of the asperities was established,and based on the distribution of the island area The function establishes the theoretical contact model of the rough surface.Based on the theoretical contact model established above,considering the actual situation of the dry-gas seal friction contact interface,a dry-gas seal normal contact stiffness model is established.The results show that the normal contact stiffness is positively correlated with the fractal dimension and negatively correlated with the characteristic scale.With the increase of fractal dimension,the normal contact stiffness increases by an order of magnitude;with the increase of the feature scale,the normal contact stiffness gradually decreases,and the order of magnitude of the normal contact stiffness also decreases;the normal contact stiffness and the real contact area It is positively correlated,and gradually increases with the increase of the real contact area,and the increase range decreases in turn;Based on Hertz’s contact theory,Coulomb’s friction law and the theoretical analysis of the slip zone and the stick zone,a tangential stiffness model of the dry gas seal friction interface considering the elastoplastic deformation stage is established.The results show that the tangential contact stiffness is positively correlated with the fractal dimension and negatively correlated with the characteristic scale.When the fractal dimension is small,the tangential contact stiffness increases linearly;when the fractal dimension is large,the tangential contact stiffness increases nonlinearly;when the characteristic s cale is small,the tangential contact stiffness increases linearly,and this trend It is related to the fractal dimension,the larger the fractal dimension,the more obvious this trend is;The contact stiffness model established in this paper considering t he elastic-plastic deformation stage is double verified by theoretical verification and experimental verification.The normal contact stiffness model and tangential contact stiffness model established in this paper are compared and verified with the classical model and related experiments respectively.The results show that the model established in this paper has the same trend as the classical model and related experimental data,and the model in this paper is closer to the experimental value.Therefore,the model established in this paper meets the requirements of continuous smoothness,which proves the accuracy and reliability of the model in this paper.